For what value of c are the three points (-3,1), (5,5), and (6,c) on the same line?
+2864 hint:
use slope formula.
Make sure all the points have the same slope
The slope between the points (-3,1) and (5,5) is 8/4 = 2. Then by point-slope form, the equation of the line is y - 1 = 2(x + 3), or y = 2x + 7. So when x = 6, c = 2*6 + 7 = 19.
+26393 For what value of c are the three points (-3,1), (5,5), and (6,c) on the same line?
\(\begin{array}{|rcll|} \hline \dfrac{c-5}{6-5} &=& \dfrac{5-1}{5-(-3)} \\\\ c-5 &=& \dfrac{4}{8} \\\\ c-5 &=& \dfrac{1}{2} \\\\ c &=& 5+ \dfrac{1}{2} \\\\ \mathbf{c} &=& \mathbf{5.5} \\ \hline \end{array}\)
